Convertible Senior Notes - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Debt Disclosure [Abstract]
Amortization of debt discount	$ 463	$ 449	$ 1,377	$ 1,079
Amortization of debt issuance costs	4,881	4,712	14,515	11,373
Capitalization of interest expense	(714)	(679)	(2,008)	(1,513)
Interest expense	$ 4,630	$ 4,482	$ 13,884	$ 10,939